Improper initialization in Linux kernel - CVE-2026-90211

Vulnerability details

The vulnerability allows a local user to cause BPF programs to retain stale register values after faulting atomic operations.

The vulnerability exists due to improper initialization in bpf_jit_probe_atomic_pre() in the s390 BPF JIT compiler when processing faulting BPF_PROBE_ATOMIC read-modify-write operations. A local user can execute a BPF program containing a faulting arena atomic operation to cause BPF programs to retain stale register values after faulting atomic operations.

Only read-modify-write atomic operations carrying BPF_FETCH and BPF_CMPXCHG read an old value into a register.

Affected software

How to mitigate CVE-2026-90211

External References

• https://git.kernel.org/stable/c/1a26541b3f60ce447433a4c4dd56edb10d2cd580
• https://git.kernel.org/stable/c/44b702fceb4cf3a4ddbfb496f487b034814bf1a3
• https://git.kernel.org/stable/c/cc3e12330599f097f0e1f792435686ddc276f26d

Related Security Bulletins

• Improper initialization in Linux kernel s390 net
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more